The references to Volumes 2, 4, 10 are to the editions of 1897, 1895, and 1881: other editions of these volumes differ in pagination and to some extent in contents.

If the Index is used with Volume 2, edition 1879, in introduction after p. xiv deduct from one to five pages, and in text deduct after page 99 from one to three pages; if with Volume 10, edition 1898, add in part I in introduction eight pages, and in text after page 48 one page; in part II after page 35 deduct one page to eleven pages, increasing the allowance gradually through the part.